1. Field of Invention
The present invention relates to micro-electromechanical systems (MEMS) structure. More particularly, the present invention relates to MEMS structure with a sensing diaphragm.
2. Description of Related Art
The sensitivity of a MEMS structure, such as MEMS microphone, is strongly dependent on the residual stress of the diaphragm in the MEMS structure. The residual stress of a diaphragm varies with the fabrication process including the different thermal expansion between different materials, non-uniform micro-structure in single material during growth and others like package, operation environment, etc.
To design a diaphragm which can reduce the effect of the residue stress becomes an important task. Conventionally, several trench rings are formed at the peripheral region of the diaphragm to absorb the residue stress.